1. Field of the Invention
The present invention relates to a downhole tool for assisting in separating and reconnecting well tubing and, more particularly, to a polished bore and anchor seal assembly that has a mechanism to prevent seal damage.
2. Description of Related Art
A wellbore production tubing string has several different types of devices that are attached thereto and which are necessary to the operation of the well. For example: an expansion joint can be used to accommodate length changes in the tubing due to thermal or pressure fluctuations; or a device to establish communication between the tubing string and the wellbore annulus, commonly referred to as a sliding sleeve or sliding side door may be used; and by statute, all offshore wells are required to have an operational subsurface safety valve. Additionally, if the well bore requires artificial lift, a gas lift mandrel or an electric submersible pump can be used. Any or all of the above described devices may be required to be removed for periodic maintenance or repair. To effect repair of these devices, removal of the production tubing string is necessary.
The task of removing the production tubing is complicated by its attachment to packers and the inherent difficulty in disengaging or releasing the packer. To overcome this problem, devices have been designed to allow for the separation of tubing so that some items may be easily left in the well bore while others items are removed. Several of such separation type devices are described in the 1986 "Packers And Completion Accessories Catalog" published by Camco Products & Services Company, a division of Camco International, Inc. One such device is described on Page 26 of that catalog, and is referred to as a "stinger", but is also commonly referred to as an "anchor seal assembly", and contains several latching configurations, a set of chevron packing seals and a metallic body mandrel to resist applied pressure and tensile loads. This device stabs into, latches and seals at the top of a wellbore packer. A second device of this type is shown on Page 62 of the same catalog, and is called a Type A Safety joint. This device has a coarsely pitched left handed thread, and O-ring seals so that the tubing can be separated by torque applied in the right hand or clockwise direction. Other similar devices are further described in that catalog.
An inherent problem in each of these devices is in reestablishing the connection and effecting a fluidic seal once disengaged without damaging the annular packing seals. This problem is exacerbated in deviated or horizontal sections of wells for the following reasons. In the case of safety joints or any such device that relies on an elastomeric O-ring to effect a seal between the upper and lower halves, separation and reconnection is not considered possible since the likelihood of damage to an essential O-ring is high in either or both operations. The stingers and related separation and relatching tools have redundant chevron seals on the upper male half of the connector but are subjected to abrasion wear against the casing when the exposed seals are dragged or pushed through horizontal or deviated well sections.
There is a need for a device to allow for the release and reconnection of the tubing from a device fixed in a well, while protecting the annular seals during removal and/or reconnection.